MICHAEL PORTILLO’S popular BBC television series ‘Great British Railway Journeys’…
Why not the Clapper bridge at Postbridge for instance?
NOT ONE of Devon’s many beautiful bridges has made it onto the Top Ten list published on the VisitBritain web site which has been busy promoting a new book called Poohstickopedia
Each bridge has been selected as being ‘perfect’ for playing Poohsticks, the game invented by Winnie the Pooh in A.A.Milne’s The House at Pooh Corner but alas there are no ‘perfect’ Devon bridges apparently.
The nearest we came to having a bridge included was one they found somewhere in Cornwall, which is much further long the A30.
Abridged too far
They even found a top engineer – Dr Rhys Morgan (a Welshman) from the Royal Academy of Engineering to devise a formula to help budding players choose a winning stick.
He said the main variables that need to be considered when designing the optimum Poohstick included cross-sectional area, density/buoyancy, and the drag coefficient and devised the formula PP = A x I x Cd where PP is Perfect Poohstick, A is cross sectional area, I is density of the stick and Cd is the drag coefficient.
We asked for a comment from a regular reader of this column, John Buckmaster, Professor Emeritus at the University of Illinois.
It’s drivel. The drag coefficient (non-dimensional) is usually defined as Drag/[0.5 \rho V V A] where \rho is the density of the fluid, V is the speed of the fluid relative to the body experiencing drag, and A is the surface area of the body. What has A, the cross-sectional area, got to do with the matter?
And a twig would, upon impact in the water, very quickly reach a speed equal to that of the water, so that V=0 and the Drag therefore equals 0.
But there is a more basic problem. The formula merely yields a number for PP. Plug in A, I, and Cd and you get a number with dimensions mass/length. To talk about a PP you need to specify the perfect value of this number, but no such number is identified.
Either Rhys Morgan is playing games with us (those darned English) or his work is misrepresented.
Thank you John. Let’s see VisitBritain poo-pooh that.
HOW TO PLAY POOHSTICKS
Competitors choose a stick each and drop them from the upstream side of a bridge. They then cross to the downstream side of to see which is first to emerge.